The proposed study on Relation of Protein Structure to Biological Function will be concerned with the properties (chemical, enzymic, conformation) of acidic proteases and their zymogens. In addition, inhibitors which combine specifically with the zymogens by forming a Schiff base (gossypol, pyridoxyl phosphate) will be used to study the activation of the precursor to the enzyme. Thus, it should be possible to identify the amino acid residues which must be accessible to react with the inhibitors and hence are essential for the activation to occur.